The present invention is directed to battery testers of the AC current load type, in general, and more particularly, to a battery tester including a voltage divider network calibrated in accordance with a predetermined battery rating scale to adjust a measured signal representative of the internal resistance of the battery under test to render a voltage potential signal which when compared to a threshold voltage potential determines the condition of the battery.
Modem AC current load type electronic battery testers, like the KM4500 manufactured by ACTRON Manufacturing, Inc. under the registered trademark KAL EQUIP, include a microcontroller with embedded software for managing the functions thereof, like keyboard sensing, display driving, and control of the analog circuitry which interface with the battery, for example. Typically, the user enters information of the battery under test using keys on a panel and reads the information through an alphanumeric display which may be of the liquid crystal type, for example. The microcontroller controls the analog circuitry coupled to the battery under test and processes the measured battery signals to determine the battery""s condition under control of the embedded software routines. While very successful, these type testers are considered at the high end of battery testing equipment spectrum due to their sophistication and multifunctional capabilities.
What is needed is a battery tester that is less sophisticated, simple to use and lower in cost to fill a void at the low end of the equipment spectrum. Through the years, some have attempted to fill this gap by offering simple electronic battery testers without utilizing a microcontroller. Examples of these simple electronic testers are found in the following U.S. Patents:
1. U.S. Pat. No. 3,909,708, issued on Sep. 30, 1975 to Champlin and entitled xe2x80x9cElectronic Battery Testing Devicexe2x80x9d;
2. U.S. Pat. No. 4,719,428, issued on Jan. 12, 1998 to Liebermann and entitled xe2x80x9cStorage Battery Condition Tester Utilizing Low Load Currentxe2x80x9d;
3. U.S. Pat. No. 4,816,768 issued on Mar. 28, 1989 to Champlin and entitled xe2x80x9cElectronic Battery Testing Devicexe2x80x9d; and
4. U.S. Pat. No. 5,592,093 issued on Jan. 7, 1997 to Klingbiel and entitled xe2x80x9cElectronic Battery Testing Device Loose Terminal Connection Detection Via A Comparison Circuitxe2x80x9d.
The present invention offers an alternative to these type electronic battery testers which is simple to use, low in cost and provides aspects not found therein.
In accordance with one aspect of the present invention, a method of measuring a condition of a battery using a measure of the internal resistance thereof comprises the steps of: inducing an AC signal across the terminals of the battery by applying an AC current load thereto; measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery""s internal resistance; applying the first voltage potential signal across a voltage divider network calibrated in accordance with a predetermined battery rating scale to render a multiplicity of second voltage potential signals at a corresponding multiplicity of taps along the voltage divider network, values of said second voltage potential signals being representative of the calibrated battery rating scale; and sequentially selecting the second voltage potential signals along the taps for comparison with a threshold voltage potential signal to determine a measure of the condition of the battery.
In accordance with another aspect of the present invention, an electronic battery in tester comprises: a first circuit for applying an AC current load to the battery under test to induce an AC signal across the terminals of the battery; a second circuit for measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery""s internal resistance; a voltage divider network coupled across the first voltage potential signal, said voltage divider network calibrated in accordance with a predetermined battery rating scale to create from the first voltage potential signal a multiplicity of second voltage potential signals at a corresponding multiplicity of taps along the voltage divider network, values of said second voltage potential signals being representative of the calibrated battery rating scale; and means for selecting the second voltage potential signal of the multiplicity of second voltage potential signals along the taps based on a predetermined battery rating of the battery under test for comparison with a threshold voltage potential signal to determine a condition of the battery.